Share to… finds the people of your workspace and its public channels, not only conversations you already have; picking a person opens New message with what you are sharing, so nothing is created before you send. Later lets go of a saved message as soon as it is deleted.
On a phone, or where your text size makes the window short, a shared channel’s banner is one line that opens its details, and the note that somebody you named is not in the channel is one line with What now?, which offers Add them, Let them know or Do nothing. The @ list puts the channel’s people first and marks the rest.
On a touch tablet held sideways, the system Back closes a docked thread or panel before it leaves the conversation. At the largest text sizes, lists and canvases keep their options and Share on screen, Catch up and Home fit a phone on its side, and Canvases shows a whole card on the smallest phones. A group’s header says you are starting a Link in the group.